如何优化JS代码？

Question

Chrome profiling say: "Not optimized: assignment to parameter in arguments object". What can i do for optimize this code?

this.buffer.forEach(function(tilepos, ypos)
{
  tilepos.forEach(function(tileinfo, xpos)
  {
    _self.tiles.putTile('ground', xpos, ypos, _self.ground);
  });
});

Answer 1

It likely does not like that you are acting on tilepos within the block.

I would recommend doing it as follows if you wish to eliminate the error, but also get a bit of a performance boost:

for(var i = 0; i < this.buffer.length; i++)
{
    for(var j = 0; j < this.buffer[i].length; j++)
    {
        _self.tiles.putTile('ground', i, j, _self.ground);
    }
}

Answer 2

You are most likely overwriting the arguments by reassigning a function parameter or an arguments element.

function f(a) {
    a = 100; // reassigns arguments[0]
};

Or

function f(a) {
    arguments[0] = 100; // same thing
};

Your code looks fine to me, so I assume the problem lies in your putTile method. If you need to reassign the function parameters, create a local copy of it:

function f(a) {
    var localA = a;
    localA = 100;
}

If you provide the putTile method then I can take a look and update my answer.